There is a strong interest in high-capacity data storage systems with fast data access due to an ever-increasing demand for data storage. Limitations in the storage density of conventional magnetic memory devices have led to considerable research in the field of optical memories. Holographic memories have been proposed to supersede the optical disc (CD-ROMs and DVDs) as a high-capacity digital storage medium. The high density and speed of holographic memory results from the use of three-dimensional recording and from the ability to simultaneously read out an entire page of data. The principal advantages of holographic memory are a higher information density, a short random-access time, and a high information transmission rate.
While holographic data storage systems have not yet replaced current CD and DVD systems, many advances continue to be made which further increase the potential of storage capacity of holographic memories. This includes the use of various multiplexing techniques such as angle, wavelength, phase-code, fractal, peristrophic, and shift. However, previous methods for recording information in highly multiplexed volume holographic elements, and for reading them out, have not proved satisfactory in terms of throughput, crosstalk, and storage capacity.
It has also been proposed to use double-sided holographic data storage device. However, issues such as crosstalk between layers, speed of data access and speed of access to the double diffractive holographic layers continue to challenge technological advances in this area.
Thus, it would be desirable to provide a diffractive holographic data storage device, which increases storage capacity by utilizing double layers of the data storage device. Also, it would be desirable to provide techniques for providing fast access to double sides and layers of a diffractive holographic data storage device. Furthermore, it will be desirable to provide a diffractive holographic data storage device, that is compatible with the traditional HYDIF multiplexing technology. The compatibility is coming from the smart association of two diffractive sides recorded with HYDIF process but allowing by an improvement a simultaneous simple reading of both faces. This association doubles the storage capacity and increase global reading speed of stored data access.